Force sensing distal femoral alignment system and method of use

ABSTRACT

Devices, systems, and methods are provided for facilitating the aligning and balancing of the knee during total knee replacement surgery. A femoral assembly is engaged with a distal femur. The positions of medial and lateral portions of the femoral assembly relative to a stationary portion of the femoral assembly can be separately adjusted to adjust the alignment of the knee. A force sensor will be provided to sense the forces in the medial and lateral portions of the knee, and the medial and lateral portions of the femoral assemblies will be adjusted so that the sensed forces are balanced. The alignment of the knee is visually verified using a knee alignment verification member coupled to the femoral assembly. The knee alignment verification member may emit laser beams along the mechanical axes of the femur and tibia, or the knee alignment verification member may couple to alignment rods aligned along these axes.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a non-provisional of, and claims the benefitof priority under 35 U.S.C. §119(e), U.S. Provisional Application No.61/109,770 (Attorney Docket No. 021976-000900US) filed Oct. 30, 2008,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates generally to medical surgical devices,systems, and methods. More specifically, the invention relates todevices, systems and methods for facilitating knee surgery procedures,in particular, knee replacement procedures.

The knee is generally defined as the point of articulation of the femurwith the tibia. Structures that make up the knee include the distalfemur, the proximal tibia, the patella, and the soft tissues within andsurrounding the knee joint, the soft tissues including the ligaments ofthe knee. The knee is generally divided into three compartments: medial(the inside part of the knee), lateral (the outside part of the knee),and patello-femoral (the joint between the kneecap and the femur). Themedial compartment comprises the medial joint surfaces of the femur,tibia, and the meniscus wedged therebetween. The lateral compartmentcomprises the lateral joint surfaces of the femur, tibia, and themeniscus wedged therebetween. The patellofemoral compartment comprisesthe joint between the undersurface of the kneecap or patella and thefemur. Four ligaments are especially important in the stability,alignment and functioning of the knee—the anterior cruciate ligament,the posterior cruciate ligament, the medial collateral ligament, and thelateral collateral ligament. In an arthritic knee, protective cartilageat the point of articulation of the femur with the tibia is often wornaway, allowing the femur to directly contact the tibia. Thisbone-on-bone contact can cause significant pain, discomfort, anddisability for a patient and will often necessitate knee replacement orknee arthroplasty.

Knee arthroplasty involves replacing the diseased and painful jointsurface of the knee with metal and plastic components shaped to allownatural motion of the knee. Knee replacement may be total or partial.Total knee replacement surgery, also referred to as total kneearthroplasty (“TKA”), involves a total replacement of the distal end ofthe femur, the proximal end of the tibia, and often the inner surface ofthe patella with prosthetic parts. Cuts are made on the distal end ofthe femur and the proximal end of the tibia. Prosthetic parts are thenattached. The prosthetic parts create a stable knee joint that movesthrough a wide range of motion. The replacement of knee structures withprosthetic parts allows the knee to avoid bone-on-bone contact andprovides smooth, well-aligned surfaces for joint movement.

In knee replacement surgeries, it is often vital to restore themechanical alignment of the knee, i.e., the proper alignment of themechanical axes of the femur and tibia with each other. Many methods anddevices currently are used to restore the mechanical alignment of theleg. These methods and devices are typically used during Total KneeReplacement surgery and include alignment rods, e.g., intramedullary andextramedullary rods, surgical navigation systems, and CT and or MRIbased “bone morphing” or ‘shape-fitting” technologies. Generally,empirical anatomical landmarks are used in these methods. Theseanatomical landmarks are either directly/mechanically observedintra-operatively, or indirectly relied upon, serving as the foundationof a computer generated reference method. Reference geometry andphysical or virtual measurements are often used to ultimately alignbone-cutting guides or templates which facilitate bone resections (madewith a surgical saw blade). These bone resections will typicallyproperly orient a knee prosthesis in the correct location/alignment.Generally, none of these methods directly take the condition ortendencies of the soft-tissue structures, such as the lateral collateraland medial collateral ligaments, about the knee into consideration.

Historically, surgeons performing total knee replacement surgery in thelate 1970s and early 1980s, would typically first resect the proximaltibia, creating a flat surface perpendicular to the shaft of the tibia.The leg was then brought to extension. Spacer blocks were shoved betweenthe resected tibia and the uncut distal femur. The spacer blocks wereselected from various thicknesses in order to distract the knee jointspace to the extent the ligaments about the knee were somewhat taut.Once the knee joint was distracted to that taut condition, a distalfemoral cutting guide was positioned in a way to yield a distal femoralbone cut parallel to the tibial cut. It was believed then, a distalfemoral bone cut using this method of distracting the joint spacebetween the tibia and femur, would yield proper alignment of themechanical axis of the leg. This method would often prove successful aspracticed by a skilled surgeon and in the case of “passive deformities”of the knee. However, the distraction method would typically not haveany accurate means of determining ligament forces between the medialside of the knee and/or the lateral side of the knee. As such, properalignment would often not be restored. Additionally, the method of firstmaking a proximal tibial bone resection and then making a distal femoralbone resection parallel to the tibial bone resection did not restoreproper alignment of the leg in the case of “fixed deformities” of theknee. The case of “fixed deformities” of the knee would otherwiserequire ligament releases to restore proper alignment of the knee.Accordingly, many early knee replacement surgeons determined the tibialbone resection and the distal femoral bone resections should be madeindependent of each other.

As technology has advanced, including the introduction of CT scannersand MRI technology, the thought of computerized bone morphing has gainedpopularity as a means to accurately place cutting guides. The cuttingguides in turn would be used in efforts to place prosthetic kneeimplants in a position in which the knee is properly aligned. Earlystudies have not found these bone morphing technologies always accurate,reporting proper alignment of the leg was not restored. However, aproper patient selection, e.g., patients with mild, passive deformitiesof the knee, might be viable candidates for bone morphing technology,assuming those patients/deformities could be properly corrected bysimple anatomical referencing, as determined by a CT or MRI scan.

However, bone morphing technology is often costly, requiring a CT or MRIscan to determine any given patient's anatomy. Electronic images fromsuch scans must be “filtered” by a computer technician. The “filtered”scan data must be electronically conveyed to some type of fabricationmachine, such as a CNC Machining Center or a Rapid Prototype Machine.Ultimately, “shape-matching” and “patient specific” cutting guides mustbe produced and delivered into surgery.

As such, there is a clear need for systems, devices, and methods of kneesurgery that can help surgeons quickly, accurately, and cost-effectivelyposition the distal femoral cutting guide, thus restoring properalignment and soft-tissue balance of the leg during total kneereplacement surgery.

2. Description of Background Art

Non-patent literature which may be of interest may include: Murray,David G., “Variable Axis™ Total Knee Surgical Technique,” HowmedicaSurgical Techniques, Howmedica Inc. 1977; Mihalko, W H et al.,“Comparison of Ligament-Balancing Techniques During Total KneeArthroplasty,” Jnl. Bone & Jt. Surg., Vol. 85-A Supplement 4, 2003,132-135; Eckhoff, D G et al., ″Three-Dimensional Morphology andKinematics of the Distal Part of the Femur Viewed in Virtual Reality,Jnl. Bone & Jt. Surg., Vol. 85-A Supplement 4, 2003, 97-104; and Ries, MD, et al., “Soft-Tissue Balance in Revision Total Knee Arthroplasty,”Jnl. Bone & Jt. Surg., Vol. 85-A Supplement 4, 2003, 38-42. Patents ofinterest may include U.S. Pat. Nos. 4,501,266; 4,646,729; 4,703,751;4,841,975; 5,116,338; 5,417,694; 5,540,696; 5,597,379; 5,720,752;5,733,292; 5,800,438; 5,860,980; 5,911,723; 6,022,377 and 6,758,850.Patents applications of interest may include co-assigned U.S. patentapplication Ser. Nos. 10/773,608, now U.S. Pat. No. 7,442,196, entitled“Dynamic Knee Balancer” (Attorney Docket No. 021976-000200US);10/973,936, now U.S. Pat. No. 7,578,821 entitled “Dynamic Knee Balancerwith Pressure Sensing” (Attorney Docket No. 021976-000210US); 11/149,944now U.S. Patent Publication Application No. 2005/0267485 A1 entitled“Dynamic Knee Balancer with Opposing Adjustment Mechanism” (AttorneyDocket No. 021976-000220US); 61/090,535 entitled “Sensing Force DuringPartial and Total Knee Replacement Surgery” (Attorney Docket No.021976-000800US); and 61/107,973 entitled “Dynamic Knee Balancing forRevision Procedures” (Attorney Docket No. 021976-000700US), the entirecontents of each of which are incorporated herein by reference.

BRIEF SUMMARY OF THE INVENTION

The present invention provides devices, systems, and methods forfacilitating a surgery performed on a knee, particularly by facilitatingthe aligning of the knee during a total knee replacement surgery. Afemoral assembly is engaged with a distal femur and placed in the gapbetween the distal femur and proximal tibia. The femoral assemblycomprises a stationary portion, an adjustable medial portion, and anadjustable lateral femoral portion. The positions of the medial andlateral femoral portions relative to the stationary portion can beseparately adjusted to adjust the varus-valgus alignment of the knee,e.g., the angle between the femur and tibia, as well as the tension inthe soft tissues adjacent the knee. Additionally, the femoral assemblycomprises adjustable posterior members that fill the posterior capsuleof the knee with a thickness similar to the prosthetic femoral implant.Typically, a force sensor will be provided to sense the forces in themedial portion of the knee and the lateral portion of the knee, and themedial and lateral femoral portions will be adjusted so that the sensedforces are balanced. A visual display may be provided to show thesurgeon the sensed forces. In addition, a thickness adapter may beprovided to removable attach to the force sensor to fill the spacebetween the femur and tibia to the point force readings are obtained.The alignment of the knee can be visually verified using a kneealignment verification member coupled to the femoral assembly, andfurther verified by angular graduation markings placed upon the femoralstationary portion. The knee alignment verification member may emitlaser beams along the mechanical axes of the femur and tibia. Or,alignment rods which align along the mechanical axes of the femur andtibia may be coupled to the knee alignment verification member. Thealignment of the knee can be verified using with the laser beams and/orthe alignment rods. When the knee is properly aligned, placement pinsmay be positioned in the distal femur guided by the femoral assembly.The femoral assembly can then be removed and a cutting guide can bepositioned on the distal femur based on the position of the placementpins. A cut parallel to a previously made cut on the tibia can then bemade on the distal femur. A prosthetic knee placed on these cuts willmaintain the proper alignment of the knee.

In a first aspect, the invention provides a system for aligning the kneeduring a surgical procedure on the knee. The system comprises a femoralassembly that is removably engaged with a distal femur. The femoralassembly includes a stationary femoral portion, an adjustable medialfemoral portion (which is coupled to the stationary femoral portion),and an adjustable lateral femoral portion (which is coupled to thestationary femoral portion. A knee alignment verification member iscoupled with the stationary femoral portion of the femoral assembly andprovides visual confirmation of a femoral and tibial mechanical axes ofthe knee. A force sensor is coupled with the stationary femoral portionof the femoral assembly. The force sensor comprises a medial portion forsensing a first force in a medial portion of the knee and a lateralportion for sensing a second force in a lateral portion of the knee.

In one embodiment, the knee alignment verification member means includesa laser knee alignment verification member is coupled to the stationaryfemoral portion. The laser knee alignment provides a first laser beamoriented along the femoral axis of the knee and a second laser beamoriented along the tibial axis of the knee.

In some embodiments, the knee alignment verification member includes amechanical knee alignment verification assembly. The mechanical kneealignment verification assembly includes a knee alignment hub. A firstrod is coupled with the knee alignment hub to be oriented along thefemoral axis of the knee and a second rod is coupled with the kneealignment hub to be oriented along the tibial axis of the knee.

In an embodiment, the adjustable medial portion includes a medial paddleand the adjustable femoral portion includes a lateral paddle.

In still other embodiments, the position of the adjustable medialfemoral portion relative to the stationary femoral portion isadjustable. The position of the adjustable lateral femoral portionrelative to the stationary femoral portion is adjustable.

In other embodiments, the adjustable medial femoral portion and theadjustable lateral femoral portion are separately adjustable.

In some embodiments, a medial rotatable screw couples the adjustablemedial femoral portion with the stationary femoral portion. A lateralrotatable screw couples the adjustable lateral femoral portion with thestationary femoral portion.

In some embodiments, rotating the medial rotatable screw adjusts theposition of the adjustable medial femoral portion relative to thestationary femoral portion. Rotating the lateral rotatable screw adjuststhe position of the adjustable lateral femoral portion relative to thestationary femoral portion.

In some embodiments, the force sensor comprises a force sensing elementselected from the group consisting of piezoelectric sensors, forcesensing resistors, force sensing capacitors, strain gages, load cells,and pressure sensors.

In still other embodiments, a processor is coupled with the force sensorfor processing sensed force data into usable data and for providing thedata to a user. A visual display is coupled with the processor andadapted to display the usable data.

In some embodiments, the visual display displays usable datarepresenting a first force sensed in the medial portion of the knee anda second force sensed in the lateral portion of the knee.

In some embodiments, the system for aligning a knee during knee surgeryincludes a plurality of locating pins. The stationary femoral portiondefines at least one medial aperture for positioning at least onelocating pin on the distal femur and at least one lateral aperture forpositioning at least a second locating pin on the distal femur.

In some embodiments of the invention, a cutting guide is removablyengaged with the distal femur. The cutting guide is positioned relativeto the distal femur based on the position of at least one first locatingpin and the at least a second locating pin.

In some embodiments, the force sensor is removably coupled to athickness adapter. The adapter fills the space between the femur andtibia.

In some embodiments, the adjustable medial femoral portion and theadjustable lateral femoral portion include a medial fulcrum and lateralfulcrum. The fulcrums are positioned against the provisionally cutdistal femur when the distal femoral alignment assembly is mountedagainst the distal femur. In other embodiments, a bone interface plateis disposed between the fulcrums and the distal femur.

In a second aspect, the invention provides a method for aligning theknee during a surgical procedure on the knee including engaging afemoral assembly with a distal femur. The femoral assembly includes astationary femoral portion, an adjustable medial femoral portion(coupled to the stationary femoral portion), and an adjustable lateralfemoral portion (coupled to the stationary femoral portion). A forcesensor is coupled with the stationary femoral portion of the femoralassembly. A first force is sensed in a medial portion of the knee and asecond force is sensed in the lateral portion of the knee using thecoupled force sensor. The position of the adjustable medial femoralportion can be adjusted separately relative to the stationary femoralportion and the position of the adjustable lateral femoral portion isseparately adjustable relative to the stationary femoral portion basedon the sensed first and second forces to align a femoral and tibialmechanical axes of the knee. The alignment of the femoral and tibialmechanical axes of the knee are visually confirmed using a kneealignment verification assembly coupled with the stationary femoralportion of the femoral assembly.

In one embodiment, a method for aligning the knee during a surgicalprocedure on the knee comprises coupling a mechanical knee alignmentverification assembly with the stationary femoral member of the femoralassembly. A first alignment rod of the mechanical knee alignmentverification assembly is aligned along the femoral axis of the knee anda second alignment rod of the mechanical knee alignment verificationassembly is aligned along the tibial axis of the knee. The femoral andtibial mechanical axes of the knee is visually confirmed by thealignment of the first alignment rod and the second alignment rodrelative to each other.

In another embodiment, a laser knee alignment verification member iscoupled with the stationary femoral member of the femoral assembly, Afirst laser beam from the laser knee alignment verification member isaligned along the femoral mechanical axis of the knee and a second laserbeam from the laser knee alignment verification member is aligned alongthe tibial mechanical axis of the knee along the tibial axis of theknee, The alignment of the femoral and tibial mechanical axes of theknee is visually confirmed by the alignment of the first laser beam andthe alignment of the second laser beam relative to each other.

In some embodiments, the positions of the adjustable medial femoralportion relative to the stationary femoral portion and of the adjustablelateral femoral portion relative to the stationary femoral portion areadjusted based on the sensed first force and the sensed second force sothat the first and second forces are balanced.

In some embodiments, the first force in a medial portion of the knee issensed and a second force in a lateral portion of the knee is sensedusing the coupled force sensor. This includes transmitting a voltage toa sensor element of a thin force sensing portion of the force sensor andmeasuring the voltage after it has passed through the sensor element.The percentage of the voltage that passed through the sensor element isdetermined relative to the voltage transmitted to the sensor element.The measured force is derived from the percentage.

In yet another embodiment, the sensed first force and the sensed secondforce is visually displayed by a display coupled to the force sensor.

In some embodiments, separately adjusting the position of the adjustablemedial femoral portion relative to the stationary femoral portion andthe position of the adjustable lateral femoral portion relative to thestationary femoral portion comprises rotating at least one of a lateralrotatable screw coupling the adjustable lateral femoral portion to thestationary femoral portion and a medial rotatable screw coupling theadjustable medial femoral portion to the stationary femoral portion.

In some embodiments, the stationary femoral portion defines at least onemedial aperture and at least one lateral aperture. The method furtherincludes positioning at least one locating pin on the distal femur basedon at least one medial aperture and positioning at least a secondlocating pin on the distal femur based on the at least one lateralaperture.

In an embodiment, the femoral assembly is disengaged with the distalfemur and engages a distal femoral cutting guide with the distal femur.The distal femoral cutting guide is positioned relative to the distalfemur based on the position of at least one first and at least onesecond locating pins.

In some embodiments, cuts are made on the distal femur based on theposition of the distal femoral cutting guide.

In another aspect, the invention provides a method for aligning a legduring knee surgery. The leg has a femur and a tibia. The femur has amechanical axis, a distal end and a proximal end. The tibia has amechanical axis, a distal end and a proximal end. The method of aligningthe leg includes engaging a femoral assembly with the provisionally cutdistal end of the femur. The femoral assembly includes a stationaryfemoral portion, an adjustable medial femoral portion that has a medialpivot fulcrum coupled to the stationary femoral portion, and anadjustable lateral femoral portion that has a lateral pivot fulcrumcoupled to the stationary femoral portion. A force sensor is coupledwith the stationary femoral portion of the femoral assembly. A medialposterior member is reversibly coupled to the medial side of thestationary femoral portion. A lateral posterior member is reversiblycoupled to the lateral side of the stationary femoral portion. Themedial member abuts the medial posterior femur and the lateral memberabuts the lateral posterior femur. A first force is sensed in a medialportion of the knee and a second force is sensed in the lateral portionof the knee using the force sensor. The position of the adjustablemedial femoral portion is adjusted relative to the stationary femoralportion and the position of the adjustable lateral femoral portion is(separately) adjusted relative to the stationary femoral portion basedon the sensed first and second forces to align the femoral and tibialmechanical axes of the knee. The alignment of the femoral and tibialmechanical axes of the knee is visually confirmed using a knee alignmentverification assembly which is coupled with the stationary femoralportion of the femoral assembly.

In one embodiment, the medial member abuts the medial posterior femurand the lateral member abuts the lateral posterior femur when the leg isfully extended.

In some embodiments, the medial and lateral fulcrums determine fixeddistance points to adjust an angle.

In some embodiments, a bone interface plate is disposed between theadjustable medial and lateral femoral portions and the distal femur.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exploded view of a distal femoral alignment componentassembly according to embodiments of the invention.

FIG. 2 shows a top view of the unadjusted distal femoral alignmentassembly of FIG. 1.

FIG. 3 shows a top view of the adjusted distal femoral alignmentassembly of FIG. 1.

FIG. 4 shows a perspective view of the unadjusted distal femoralalignment assembly of FIG. 1.

FIG. 5 shows a perspective view of the adjusted distal femoral alignmentassembly of FIG. 1.

FIGS. 6 and 7 shows perspective views of a knee alignment systemaccording to embodiments of the invention.

FIG. 8 shows a visual display of a knee alignment system according toembodiments of the invention.

FIGS. 9-10 show a side view of a knee alignment system, including thedistal femoral alignment component and the force sensor coupledtogether, being placed in the gap.

FIGS. 11-12 show a perspective view of a knee alignment system,including the distal femoral alignment component and the force sensorcoupled together, being placed in the gap.

FIGS. 13-23 show a method of aligning a knee during surgery according toembodiments of the invention.

FIG. 24A-B shows exploded views of a knee alignment system according toembodiments of the invention.

FIG. 25 shows a top view of the unadjusted distal femoral alignmentassembly.

FIGS. 26A and 26C show perspective posterior views of the unadjusteddistal femoral alignment assembly shown in FIG. 25.

FIG. 26B shows a posterior perspective of the unadjusted distal femoralalignment assemblies shown in FIGS. 26A and 26C with the bone interfaceplate removed.

FIGS. 27-35 show an alternative method of aligning a knee surgeryaccording to embodiments of the invention.

FIG. 36 is a flow chart schematically illustrating a method for aligningand balancing a knee during knee surgery according to embodiments of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention provide systems, devices, andmethods for facilitating the alignment and balancing of the knee duringknee replacement surgery and verifying such balance and alignment. Oncethe knee is properly aligned, a cut parallel to a previously made cut onthe tibia can be made on the distal femur. A prosthetic knee placed onthese cuts will maintain the proper alignment of the knee.

Referring now to FIG. 1, a distal femoral alignment assembly orcomponent 100 according to embodiments of the invention is shown in anexploded view. As shown in FIG. 1, distal femoral alignment assembly 100can be used for either the left or right knee, i.e., one side of thedistal femoral alignment assembly may be the medial side while the otheris the lateral side and vice versa. Distal femoral alignment assembly100 comprises a main body 101, an adjustable medial femoral portioncoupled to the main body, and an adjustable lateral femoral portioncoupled to the main body. When the distal femoral alignment assembly 100is coupled to a distal femur, the main body or stationary portion of thedistal femoral alignment assembly is generally stationary with respectto the adjustable medial and lateral femoral portions. The adjustablemedial and lateral femoral portions are adjusted with respect to themain body. Adjustable medial and lateral femoral portions respectivelycomprise medial and lateral paddles 102, 103. The medial and lateralpaddles each comprise anti-rotation shafts 104, 105 which fit into slots106 of the main body. Medial and lateral distraction screws 107, 108respectively couple the medial and lateral paddles 102, 103 with themain body 101. Distraction screw capture pegs 109, 110 fix the axialposition of the distraction screws 107, 108 relative to the main body101 such that rotation of the medial and lateral distraction screws onlyadjusts the positions of the adjustable medial and lateral femoralportions with respect to the main body 101. The main body comprisesmounts for attachment of a force sensor 111.

Referring now to FIG. 2, the main body 101 of the distal femoraladjustment assembly 100 further defines cutting guide locating apertureson its medial 113 a-c and lateral 112 a-c sides. These apertures arecutting guide locating means, e.g., by facilitating the placement ofplacement pins from which provide points of reference for the placementof a cutting guide. The main body further defines slots or verificationattachment slots or apertures 114 a, 114 b for attaching a kneealignment verification means as described below.

FIGS. 2 and 4 show the distal femoral adjustment assembly 100unadjusted. FIGS. 3 and 5 show the distal femoral adjustment assembly100 adjusted, i.e., the position of one paddle of the distal femoraladjustment assembly has been moved relative to the other.

FIGS. 6 and 7 show a perspective view of a knee alignment system 99 aaccording to embodiments of the invention. The system comprises thedistal femoral adjustment assembly 100 as described above. The systemfurther comprises a electronic force-sensing means or force sensor 115coupleable with the distal femoral adjustment assembly 100. As shown,the force sensor 115 comprises a handheld tool but may alternatively bea smaller device coupleable with the main body of the distal femoraladjustment assembly 100. The force sensor 115 senses the force betweenthe medial portion of the distal femur and the medial portion of thetibial plateau as well as the force between the lateral portion of thedistal femur and the lateral portion of the tibial plateau, for example,by comprising first and second force sensing portions 116 a, 116 b, thefirst force sensing portion 116 a being a lateral force sensing portionwhile the second 116 b is a medial force sensing portion and vice versa.The distal femur and tibial plateau are not shown in FIGS. 6-7. Theforce sensor 115 may be similar to those described U.S. PatentApplications Nos. 61/090,535 entitled “Sensing Force During Partial andTotal Knee Replacement Surgery” (Attorney Docket No. 021976-000800US)and 61/107,973 entitled “Dynamic Knee Balancing for Revision Procedures”(Attorney Docket No. 021976-000700US), the entireties of which had beenpreviously incorporated herein by reference.

FIG. 8 shows a visual display 117 coupleable with the force sensor 115.The visual display displays data representative of the force sensed bythe force sensor and may be similar to those described in U.S. patentapplication Ser. Nos. 10/973,936, now U.S. Pat. No. 7,578,821, entitled“Dynamic Knee Balancer with Pressure Sensing” (Attorney Docket No.021976-000210US); 61/090,535 entitled “Sensing Force During Partial andTotal Knee Replacement Surgery” (Attorney Docket No. 021976-000800US);and 61/107,973 entitled “Dynamic Knee Balancing for Revision Procedures”(Attorney Docket No. 021976-000700US), the entireties of which had beenpreviously incorporated herein by reference.

FIGS. 9-23 show a method of using an exemplary knee alignment systemduring knee replacement surgery according to embodiments of theinvention. As shown in FIGS. 9 and 11, the force sensor 115 is coupledto the distal femoral alignment assembly 100. As shown in FIGS. 10 and12, the distal femoral alignment assembly 100 and the coupled forcesensor 115 are placed in the gap 120 between the distal femur 118 andthe tibial plateau 121 of the knee. As shown in FIG. 13, the forcesensor 115 senses the forces between the lateral and medial portions ofthe distal femur and the tibial plateau. The visual display 117 showsthe sensed forces (as an example, the display shows the forcesunbalanced). An adjustment wrench 122 is coupled to a rotatabledistraction screw 107 of the distal femoral alignment assembly 100. Asshown in FIG. 14, when the unadjusted distal femoral alignment assembly100 and the coupled force sensor 115 are first placed in the gap 120between the distal femur 118 and the tibial plateau 121, the knee may bemisaligned, i.e., the femoral axis and the tibial axis are not alignedwith each other as in a normal knee. As shown in FIG. 14, the bottomsurface of the distal femoral alignment assembly is 80° relative to themechanical axis 123 of the femur 118. As shown in FIG. 15, at least oneof the rotatable screws 107, 108 is rotated with the adjustment wrench122 to adjust the relative position of the adjustable medial and/orfemoral portions and to correct the alignment of the knee. Generally, bybalancing the sensed forces in the medial and lateral portions of theknee, correct alignment of the knee can be achieved (as shown in thevisual display). For example, as shown in FIG. 16, the distal femoralalignment assembly 100 has been adjusted so that the bottom surface ofthe distal femoral alignment assembly is 85° relative to the mechanicalaxis 123 of the femur 118.

The system will typically further comprise a knee alignment verificationmeans to verify the alignment of the knee by verifying the angle formedby the mechanical axes of the femur and tibia. As shown in FIGS. 17 and18, the knee alignment verification means may be a laser knee alignmentverification member 124 coupleable to the main body of the distalfemoral alignment member 100. As shown in FIG. 18, the laser kneealignment verification member 124 emits a femoral laser beam 125 a to bealigned along the mechanical axis 123 a of the femur and a tibial laserbeam 125 b to be aligned along the mechanical axis 123 b of the tibia.The angle of the femoral laser beam and the tibial laser beam relativeto each other can be used by the surgeon to verify the proper anatomicalalignment of the knee, i.e., the angle between the mechanical axes 123a, 123 b of the femur and tibia. Alternatively, as shown in FIGS. 19 and20, the knee alignment verification means may be a mechanical kneealignment verification assembly 126. The mechanical knee alignmentverification assembly 126 comprises a mechanical knee alignmentverification hub 127, a femoral alignment rod 128 coupleable with thehub 127, and a tibial alignment rod 129 coupleable with the hub 127. Thecoupled femoral alignment rod 127 can be aligned along the mechanicalaxis 123 a of the femur 118. The coupled tibial alignment rod 129 can bealigned along the mechanical axis 123 b of the tibia 119. The angle ofthe femoral alignment rod 128 and the tibial alignment rod 129 relativeto each other can be used by the surgeon to verify proper alignment ofthe knee.

As shown in FIG. 21, the system may further comprise a plurality oflocating pins 130 a, 130 b. When the knee is properly aligned, at leastone locating pin (130 a and/or 130 b) may be placed on the medial sideof the distal femur 118 and at least one locating pin may be placed onthe lateral side of the distal femur as guided by the apertures of thedistal femoral alignment assembly. As shown in FIG. 22, once thelocating pins 130 a, 130 b are placed on the distal femur 118, thedistal femoral alignment assembly 100 may be disengaged from the distalfemur.

As shown in FIG. 23, the system may further comprise a distal femoralcutting guide 131 which can be coupled to the distal femur 118 andpositioned based on the position of the locating pins 130 a, 130 b. Cutsare made on the distal femur 118, for example, with a surgical sawblades 132. Typically, these cuts will form the basis for positioning ofthe femoral portion of an artificial knee. Exemplary surgical saw bladeswhich may be used to make these cuts on the distal femur are describedco-assigned U.S. Pat. Nos. 6,022,353; 6,503,253; and 6,723,101, theentire contents of which are incorporated herein by reference.

Referring now to FIGS. 24A-B, an alternative distal femoral alignmentsystem 99 b is shown including cutting guide 131 for making aprovisional cut on the distal femur in order to mount the distal femoralalignment assembly 100 flush against the provisionally cut distal femur.As shown in FIG. 25, angular graduation marks 133 are provided. Thegraduation marks correspond to movement created by adjusting either themedial or lateral distraction paddles 102, 103 as shown in FIG. 26B. Forclarity purposes, a right distal femur is shown in FIGS. 27-28 and 34-35and a right knee joint with femur and tibia is shown in FIGS. 29-33. Themedial side of components or assemblies of the distal femoral alignmentsystem shown in FIG. 24 are hereby described either medial or lateralbased on their position when used on a right knee. Of course, theinvention can be used on the left and/or right knees. Convex shapedpivot fulcrums 500 a, 500 b are provided on the surfaces of thedistraction paddles 102, 103 which directly contact the provisionallycut distal femur when the distal femoral alignment assembly 100 ismounted against the distal femur 118. The curved surface of thedistraction paddles 102, 103 creates fixed distance fulcrum points todetermine how much angle is being adjusted. FIGS. 26A and 26C showanother embodiment of the distal femoral alignment assembly 100 of thealternative distal femoral alignment system 99 b shown in FIG. 24, whichincludes bone interface plate 137. This plate 137 provides protectionfrom convex shaped distraction paddles 102 and 103 from indenting thesofter cancellous bone exposed as a result of a provisional cut beingmade on the distal femur 118 (not shown in FIG. 26). FIG. 26C shows thebone interface plate 137 sitting on top of convex shaped distractionpaddles 102 and 103 in their unadjusted position. Shoulder screw 138 isshown, which slips through a loosely fitted hole 139 in bone interfaceplate 137 to allow for tilting of bone interface plate 137 when convexshaped distraction paddles 102 and 103 are adjusted from theirunadjusted position to an adjusted position. Spacing between convexshaped adjustment paddles 102 and 103 is maintained in themedial-lateral direction to provide for a known pivot fulcrum betweenthe two convex shaped adjustment paddles, which corresponds to angulargraduations 133 shown in FIG. 25. The angular gradations provide anindication of the angle between the femur and tibia

Referring now to FIGS. 27-35, a method of using an exemplary kneealignment system used during knee replacement surgery is shown accordingto embodiments of the invention. For purposes of clarity, a bone cut hasalready been made on the proximal tibia 119 prior to the methodsdescribed in FIGS. 27-35. FIG. 27 shows provisional distal femoralcutting guide 131 moveably attached to the provisionally cut distalfemur 118 via two pins 130 a and 130 b. FIG. 28 shows provisionalfemoral cutting guide 131 and pins 130 a and 130 b now having beenremoved and femoral anterior-posterior cutting guide 134 is nowremovably attached to distal femur 118. Saw blade 132 is shown and theanterior and posterior bone cuts are performed on distal femur 118. FIG.29 shows now the “extension gap” with the proximal tibial cut havingbeen made and a provisional distal femoral cut having been made. Theposterior femoral cut has also been made but hidden from view in FIG.29. The anterior cut has also been made on distal femur 118.

Moving now to FIG. 30, the distal femoral alignment assembly 100 andother components of the distal femoral alignment system 99 b are shownbetween the proximal tibia 119 and the distal femur 118, with the leg infull extension. Thickness adapter 133 is shown moveably coupled to forcesensor 115, and force sensor 115 is moveable coupled to distal femoralassembly 100. Adjustable posterior member 135 a is shown adjacent to alongitudinal slot 400 open on the posterior side of distal femoralassembly 100, with the slot closed on the anterior side of the distalfemoral assembly 100. FIG. 31 shows adjustable posterior member 135 ahaving now been moveably coupled within the longitudinal slot 400 alongthe medial side of distal femoral assembly 100. Moveable coupling means136 a, 136 b can include magnets or other common coupling means such asscrews or spring clips. Longitudinal slots are also provided on theopposite side of the distal femoral assembly 100. Longitudinal slotsalong the sides of distal femoral assembly 100 are of adequate length toallow for anterior-posterior adjustment of adjustable posterior memberto abut the previously made posterior cut 401 of the distal femur 118.The adjustable posterior members further balance extension filling theposterior space with a condylar thickness similar to the posteriorcondylar thickness of the femoral component to be implanted thus takinginto account soft-tissue tendencies, or bias. FIG. 32 shows componentsand assemblies of the distal femoral alignment system 99 b nowcompletely in place between the proximal tibia and the distal femur andforce readings coupled from force sensor 115 are being displayed ondisplay 117, It is understood that display 117 may be integral to forcesensor 115. The display 117 can also be separable from the sensor. Thedisplay 117 is showing force readings of 5 and 2 lateral and medialrespectively, indicating lower force between the medial side of thedistal femur and the medial side of the proximal tibia, in this example.Adjustment wrench 122 is shown in line with the medial distraction screw107. FIG. 33 shows the medial distraction paddle 102 having now beenadjusted to a point wherein the forces being measured by sensor 115 anddisplayed by display 117 read 5 on both the lateral and the medial side.Pin 130 a is shown being driven through a lateral side cutting guidelocating aperture and pin 130 b has yet to be driven through the medialside cutting guide locating aperture. FIG. 34A shows both pins havingnow been driven through cutting guide locating apertures of distalfemoral assembly 100, and distal femoral assembly 100 now having beenremoved from the distal femur 118. Cutting guide 131 b is positionedover pins 130 a and 130 b. FIG. 34B shows cutting guide 131 b nowpositioned over pins 130 a and 130 b and saw blade 132 will be used tomake the final distal femoral cut at an angle “A” which is the plane ofbalanced resection as determined by the force sensor. FIG. 35 showsfemoral anterior-posterior cutting guide 134 now removably coupled todistal femur 118 and saw blade 132 is shown making a final cut on theanterior distal femur. Anterior and posterior chamfer cuts will also bemade on the distal femur 118 at this point.

While the above is a complete description of the preferred embodimentsof the invention, various alternatives, modifications, and equivalentsmay be used. Therefore, the above description should not be taken aslimiting in scope of the invention which is defined by the appendedclaims.

1. A system for aligning the knee during a surgical procedure on theknee, the system comprising: a femoral assembly removably engagable witha distal femur, the femoral assembly including a stationary femoralportion, an adjustable medial femoral portion coupled to the stationaryfemoral portion, and an adjustable lateral femoral portion coupled tothe stationary femoral portion; a knee alignment verification membercoupleable with the stationary femoral portion of the femoral assemblyand providing visual confirmation of a femoral and tibial mechanicalaxes of the knee; and a force sensor coupleable with the stationaryfemoral portion of the femoral assembly, the force sensor comprising amedial portion for sensing a first force in a medial portion of the kneeand a lateral portion for sensing a second force in a lateral portion ofthe knee.
 2. The system of claim 1, wherein the knee alignmentverification member means includes a laser knee alignment verificationmember coupleable to the stationary femoral portion and providing afirst laser beam oriented along the femoral axis of the knee and asecond laser beam oriented along the tibial axis of the knee.
 3. Thesystem of claim 1, wherein the knee alignment verification memberincludes a mechanical knee alignment verification assembly, themechanical knee alignment verification assembly comprising: a kneealignment hub; a first rod coupleable with the knee alignment hub to beoriented along the femoral axis of the knee; and a second rod coupleablewith the knee alignment hub to be oriented along the tibial axis of theknee.
 4. The system of claim 1, wherein the adjustable medial portioncomprises a medial paddle, and the adjustable femoral portion comprisesa lateral paddle.
 5. The system of claim 1, wherein the position of theadjustable medial femoral portion relative to the stationary femoralportion is adjustable, and the position of the adjustable lateralfemoral portion relative to the stationary femoral portion isadjustable.
 6. The system of claim 5, wherein the adjustable medialfemoral portion and the adjustable lateral femoral portion areseparately adjustable.
 7. The system of claim 5, wherein a medialrotatable screw couples the adjustable medial femoral portion with thestationary femoral portion, and a lateral rotatable screw couples theadjustable lateral femoral portion with the stationary femoral portion.8. The system of claim 7, wherein rotating the medial rotatable screwadjusts the position of the adjustable medial femoral portion relativeto the stationary femoral portion, and rotating the lateral rotatablescrew adjusts the position of the adjustable lateral femoral portionrelative to the stationary femoral portion.
 9. The system of claim 1,wherein the force sensor comprises a force sensing element selected fromthe group consisting of piezoelectric sensors, force sensing resistors,force sensing capacitors, strain gages, load cells, and pressuresensors.
 10. The system of claim 1, further comprising: a processorcoupled with the force sensor for processing sensed force data intousable data for providing to a user; and a visual display coupled withthe processor and adapted to display the usable data.
 11. The system ofclaim 10, wherein the visual display displays usable data representing afirst force sensed in the medial portion of the knee and a second forcesensed in the lateral portion of the knee.
 12. The system of claim 1,further comprising a plurality of locating pins, and wherein thestationary femoral portion defines at least one medial aperture forpositioning a first at least locating pin on the distal femur and atleast one lateral aperture for positioning a second at least onelocating pin on the distal femur.
 13. The system of claim 12, furthercomprising a cutting guide removably engagable with the distal femur,the cutting guide being positioned relative to the distal femur based onthe position of at least one first locating pin and the at least onesecond locating pin.
 14. The system of claim 1, wherein the force sensoris removably coupleable to a thickness adapter, the adapter configuredto fill the space between the femur and tibia.
 15. The system of claim1, wherein the adjustable medial femoral portion and the adjustablelateral femoral portion include a medial fulcrum and lateral fulcrum,the fulcrums positionable against the provisionally cut distal femurwhen the distal femoral alignment assembly is mounted against the distalfemur.
 16. The system of claim 15, wherein a bone interface plate isdisposed between the fulcrums and the distal femur.
 17. A method foraligning the knee during a surgical procedure on the knee, the methodcomprising: engaging a femoral assembly with a distal femur, the femoralassembly including a stationary femoral portion, an adjustable medialfemoral portion coupled to the stationary femoral portion, and anadjustable lateral femoral portion coupled to the stationary femoralportion; coupling a force sensor with the stationary femoral portion ofthe femoral assembly; sensing a first force in a medial portion of theknee and a second force in the lateral portion of the knee using thecoupled force sensor; separately adjusting the position of theadjustable medial femoral portion relative to the stationary femoralportion and the position of the adjustable lateral femoral portionrelative to the stationary femoral portion based on the sensed first andsecond forces to align a femoral and tibial mechanical axes of the knee;and visually confirming the alignment of the femoral and tibialmechanical axes of the knee using a knee alignment verification assemblycoupleable with the stationary femoral portion of the femoral assembly.18. The method of claim 17, further comprising: coupling a mechanicalknee alignment verification assembly with the stationary femoral memberof the femoral assembly; aligning a first alignment rod of themechanical knee alignment verification assembly along the femoral axisof the knee; and aligning a second alignment rod of the mechanical kneealignment verification assembly along the tibial axis of the knee,wherein visually confirming the alignment of the femoral and tibialmechanical axes of the knee comprises visually confirming the alignmentof the first alignment rod and the second alignment rod relative to eachother.
 19. The method of claim 17, further comprising: coupling a laserknee alignment verification member with the stationary femoral member ofthe femoral assembly; aligning a first laser beam from the laser kneealignment verification member along the femoral mechanical axis of theknee; and aligning a second laser beam from the laser knee alignmentverification member along the tibial mechanical axis of the knee alongthe tibial axis of the knee, wherein visually confirming the alignmentof the femoral and tibial mechanical axes of the knee comprises visuallyconfirming the alignment of the first laser beam and the alignment ofthe second laser beam relative to each other.
 20. The method of claim17, wherein the positions of the adjustable medial femoral portionrelative to the stationary femoral portion and of the adjustable lateralfemoral portion relative to the stationary femoral portion are adjustedbased on the sensed first force and the sensed second force so that thefirst and second forces are balanced.
 21. The method of claim 17,wherein sensing a first force in a medial portion of the knee and asecond force in a lateral portion of the knee using the coupled forcesensor comprises: transmitting a voltage to a sensor element of a thinforce sensing portion of the force sensor; measuring the voltage afterit has passed through the sensor element; determining a percentage ofthe voltage passed through the sensor element relative to the voltagetransmitted to the sensor element; and deriving the measured force fromthe percentage.
 22. The method of claim 17, further comprisingdisplaying the sensed first force and the sensed second force with avisual display coupled to the force sensor.
 23. The method of claim 17,where separately adjusting the position of the adjustable medial femoralportion relative to the stationary femoral portion and the position ofthe adjustable lateral femoral portion relative to the stationaryfemoral portion comprises rotating at least one of a lateral rotatablescrew coupling the adjustable lateral femoral portion to the stationaryfemoral portion and a medial rotatable screw coupling the adjustablemedial femoral portion to the stationary femoral portion.
 24. The methodof claim 17, wherein the stationary femoral portion defines at least onemedial aperture and at least one lateral aperture, the method furthercomprising positioning a first at least one locating pin on the distalfemur based on the at least one medial aperture and positioning a secondat least one locating pin on the distal femur based on the at least onelateral aperture.
 25. The method of claim 24, further comprisingdisengaging the femoral assembly with the distal femur and engaging adistal femoral cutting guide with the distal femur, the distal femoralcutting guide being positioned relative to the distal femur based on thepositioned first and second at least one locating pins.
 26. The methodof claim 25, further comprising making cuts on the distal femur based onthe position of the distal femoral cutting guide.
 27. A method foraligning a leg having a femur and a tibia during knee surgery, the femurhaving a mechanical axis, a distal end and a proximal end and the tibiahaving a mechanical axis, a distal end and a proximal end, the methodcomprising: engaging a femoral assembly with the provisionally cutdistal end of the femur, the femoral assembly including a stationaryfemoral portion, an adjustable medial femoral portion having a medialpivot fulcrum coupled to the stationary femoral portion, and anadjustable lateral femoral portion having a lateral pivot fulcrumcoupled to the stationary femoral portion; coupling a force sensor withthe stationary femoral portion of the femoral assembly; reversiblycoupling a medial posterior member to the medial side of the stationaryfemoral portion; reversibly coupling a lateral posterior member to thelateral side of the stationary femoral portion; abutting the medialmember against the medial posterior femur; abutting the lateral memberagainst the lateral posterior femur; sensing a first force in a medialportion of the knee and a second force in the lateral portion of theknee using the coupled force sensor; separately adjusting the positionof the adjustable medial femoral portion relative to the stationaryfemoral portion and the position of the adjustable lateral femoralportion relative to the stationary femoral portion based on the sensedfirst and second forces to align the femoral and tibial mechanical axesof the knee; and visually confirming the alignment of the femoral andtibial mechanical axes of the knee using a knee alignment verificationassembly coupleable with the stationary femoral portion of the femoralassembly.
 28. The method of claim 27, wherein the abutting occurs withthe leg in full extension.
 29. The method of claim 27, wherein themedial and lateral fulcrums determine fixed distance points to adjust anangle.
 30. The method of claim 27, wherein a bone interface plate isdisposed between the adjustable medial and lateral femoral portions andthe distal femur.